The present invention relates to a process for the recovery of carboxylic acids from mixtures containing glycol esters derived from these acids.
It relates more particularly to the recovery of carboxylic acids present in the heavy residues which are obtained in the epoxidation of olefines by means of the corresponding percarboxylic acids, and which contain glycol esters of these carboxylic acids.
During the epoxidation of olefines by means of peroxide compounds, such as percarboxylic acids, a mixture is obtained which contains the olefine oxide, the carboxylic acid, the solvent, if appropriate, the unconverted reactants and also various by-products including esters of the carboxylic acid. These esters are probably formed by various secondary reactions involving the olefine oxide produced and the carboxylic acid corresponding to the percarboxylic acid employed. These secondary reactions can take place both in the epoxidation reactor and in the installation used for separating the mixture originating from the epoxidation reactor. Thus, during the epoxidation of propylene with perpropionic acid, the formation of substantial amounts of propylene glycol mono- and di-propionates is observed, and this leads to a loss of reactants.
In an attempt to overcome this disadvantage, a process has been proposed, the object of which is essentially to obtain propylene glycol dipropionate (Belgian Pat. No. 841,201, filed on Apr. 28, 1976 in the names of BAYER AG and DEGUSSA). Obviously, this process does not make it possible to reduce the loss of reactants and exhibits the disadvantage of the inevitable production of propylene glycol dipropionate.